[The drug susceptibility pattern of the presumed etiologic agents of infectious enteritis including verotoxin-producing Escherichia coli O-157].

The drug susceptibility patterns were investigated for verotoxin-producing Escherichia coli (VTEC) including O-157, Salmonella spp., Vibrio parahaemolyticus and Campylobacter jejuni subsp. jejuni that were obtained in and after July 1996. The results are summarized as follows; 1. We found highly resistant strains of VTEC to tetracycline (TC) and ampicillin (ABPC). Minimum inhibitory concentrations (MIC) of some of the drugs against VTEC in an aerobic condition were significantly different from those in an anaerobic condition. For example, aerobic.anaerobic MIC ranges of the drugs tested were as follows: chroramphenicol (CP): 1.56-3.13 micrograms/ml.0.78-1.56 micrograms/ml, TC: 1.56-> 100 micrograms/ml.0.78-> 100 micrograms/ml, minocycline (MINO): 1.56-12.5 micrograms/ml.0.78-3.13 micrograms/ml, kanamycin (KM): 3.13-6.25 micrograms/ml.25-100 micrograms/ml, fosfomycin (FOM): 3.13-25 micrograms/ml.0.78-6.25 micrograms/ml, norfloxacin (NFLX): < or = 0.025-0.2 microgram/ml.< or = 0.025-0.2 microgram/ml, ABPC: 1.56-> 100 micrograms/ml.0.78-> 100 micrograms/ml and cefaclor (CCL): 1.56-25 micrograms/ml.56-12.5 micrograms/ml. MICs of CP and tetracyclines (TCs) in an anaerobic condition were lower by twofold and the MIC of FOM was lower by fourfold, but the variabilities of MIC-ranges of NFLX, ABPC and CCL were small. The MIC of KM was high. 2. We observed that some of Salmonella spp. were highly resistant to CP, TCs and MINO, and some were moderately resistant to NFLX. 3. The detection frequency of TC-resistant strains and NFLX-insensitive or resistant strains were high among C. jejuni subsp. jejuni. 4. Strains of V. parahaemolyticus and C. jejuni subsp. jejuni were mostly resistant to ABPC and CCL, MICs of which were in high ranges. 5. Fecal concentrations in MINO, KM, FOM and NFLX reported in literatures are high enough to have some antimicrobial activities, leed dose of ABPC and CCL are quite low.